Cylindromas typically occur on the head and neck of elderly females, as in this case. When large and on the scalp, the unflattering term "turban tumor" has been used. They are almost exclusively benign, even the large tumors, although rare malignant forms have been described. The etiology is controversial, derived from the sudoriferous glands with proponents on both the apocrine and eccrine sides. The histology in this case is typical. The basaloid islands fit together in a "jigsaw" pattern. A thick pink peripheral basement membrane is typical. The differential diagnosis may include eccrine spiradenoma, but these do not typically have the molded basophilic islands.
Histologic sections of skin show a dermal basophilic tumor with an overlying grenz zone. The lesion consists of variably-sized basophilic islands molding together in a characteristic "jigsaw" fashion. The islands are separated by a thick, pink basement membrane.